Field of the Disclosure
This application relates generally to improvements to a speed sensor. More particularly the present disclosure relates to improvement in functions performed by the speed sensor employing a magnet separated from a vehicle component by an air gap.
Description of the Related Art
Speed sensor and accelerometers are commonly used in an automobile for controlling vehicle systems such as anti-lock braking system, detecting and monitoring vibrations, stabilization etc. The sensors send signals to an electronic control unit (ECU), where the controlling action can be determined. Further, for increasing the stability of a vehicle, it is desired that the road surface condition, or tire condition be estimated with accuracy in real-time. The estimated road condition or tire condition is then fed back to electronic control unit to determine the optimum control action. For example, if the road surface condition is slippery then it may be necessary to operate the advanced control such as ABS (antilock braking system) braking before taking any sudden avoidance action.
The road condition and vehicle condition data can also be used for scheduling vehicle maintenance, replacing faulty parts, alerting the driver of critical condition such as brake wobble or slippery road condition, etc. Typically, several sensors are required to determine the road and vehicle conditions which can significantly increase the manufacturing and maintenance cost of the vehicle. For a low cost system, smart sensors which can perform several of the ECU functions are needed.
Road conditions can be determined in several ways using one or more sensors, and by processing the sensor signals. In U.S. Pat. No. 8,942,861 B2, a multi-sensor system having a wheel speed sensor, an accelerometer and ECU are used to determine road surface condition resulting in high system cost. The road surface condition is correlated to the speed, speed variation, acceleration and acceleration variation.
In U.S. Pat. No. 8,868,290 B2, a tire pressure monitoring system is disclosed that considers only resonant frequencies and specifically monitors tire pressure. Further, only resonant frequencies are communicated with the vehicle so the manufacturer must spend extra resources to develop logic for determining tire pressure and road conditions.
There remains a continuing need to provide an improved smart sensor which can combine multiple functions into a single speed sensor to determine tire pressure, tire concentricity, tire balance, tire flat detection, suspension damper condition, brake condition, road condition, etc. Further, the smart sensor should have an increased accuracy and reliability of tire, suspension and road condition judgment. The smart sensor should capture high frequency road inputs to wheel/suspension system that are often overlooked. Furthermore, there is a need to minimize the number of sensors by combining several functionalities into one smart sensor. For example, speed sensor that eliminates the need for an accelerometer thus reducing the system cost.